1. Field of the Invention
Embodiments of the present invention relate to an injection blow molding apparatus and method for forming molded articles.
2. Description of the Related Art
Injection blow molding (IBM) is a technique used for creating various containers such as plastic bottles for medication or other contents. The IBM process is performed with an IBM machine that first injection molds a resin into a plurality of parisons of desired shapes and then blow molds the parisons into the final molded articles.
An injection station of the IBM machine typically includes a split parison mold assembly that defines a plurality of cavities within which the parisons are formed. In the injection molding stage of the IBM process, the parison-forming surfaces of the split parison mold are heated to and/or cooled to different temperatures via a plurality of water lines formed in the split parison mold near the parison-forming surfaces. The water lines may be supplied with water at different temperatures depending on the location of the water line relative to the neck or body of the parison being formed. Typically, a plurality of individual thermolators are required to control the temperature of water supplied to the various water lines in the parison mold and an operator is required to use a significant amount of discretion in making adjustments to the water temperature flowing through water lines at different locations along the body and/or neck of the parison during the injection blow molding process.
The operator discretion necessary to make certain parison mold designs function properly requires highly experienced IBM operators and can require significant trial and error in order to determine satisfactory operating parameters. Further, the complexity of manufacturing and operating split parison molds with multiple water lines formed therein can result in high capital costs, high operating costs, and high maintenance costs.
Thus, it would be desirable to have an injection molding system and/or process where IBM operator discretion is minimized, trial-and-error operation of the IBM operator is minimized, and mold tooling design, fabrication, replacement, and maintenance costs are minimized.
Additionally, individual parison molds halves are often connected to a die set via a keyway. Once the individual parison molds halves have been slid onto the keyway, they are positioned adjacent one another and connected to one another by extending an elongated horizontal member (e.g., a length of “all thread rod”) through all the individual molds and compressing the individual molds halves against one another using the horizontal member.
This conventional configuration for connecting parison molds halves to the die set and to one another has several disadvantages. For example, the width of each individual mold half must be maintained within very tight tolerances to ensure proper alignment between individual top and bottom mold halves. Further, during operation, the series of side-by-side individual mold halves are subject to significant thermal expansion, which can cause misalignment of the top and bottom mold halves and can also cause misalignment with the core rods and/or injection nozzles that must mate with the molds as they close. An additional disadvantage of this conventional configuration is that replacement of a single mold half requires disconnection and reconnection of multiple mold halves.
Thus, it would be desirable to have an injection molding system and/or process where the parison molds are configured in a manner that mitigates the negative effects of thermal expansion and also permits easy attachment and detachment of a portion of the mold halves without requiring disconnection of all the mold halves.